It is known that compounds of the stilbene class are capable of inhibiting the growth of hormone-dependent breast tumor cells. However, such compounds, e.g., diethylstilbestrol, generally possess a number of side effects, which are explained in part through their estrogenic properties. While retaining the stilbene nature, it has been possible in some cases to modify the structure to such an extent that, in spite of tumor-inhibiting effect, the estrogenic action was still present in only weakened form. Examples of these compounds that have already found their way into therapy are TAMOXIFEN (i.e., 1-[4'-(2"-dimethylaminoethoxy)-phenyl]trans-1,2-diphenyl-1-butene) and NAFOXIDIN (i.e., 1-[4'-(2"-pyrrolidinethoxy)-phenyl]-2-phenyl-6-methoxy-3,3-dihydro-naphtha lene).
Further, it has been determined that, by displacing the hydroxyl groups in diethylstilbestrol from the positions 4,4' to the positions 3,3', one obtains a compound which possesses antiestrogenic properties at lower estrogenic activity and thus brings about an inhibition in regard to the growth of hormone-dependent breast tumor cells; see H. Schonenberger et al., Pharmazie 31, 590-597 (1976).